Method for riveting metal members therewith

ABSTRACT

A rivet and method for riveting metal members, and particularly, metal sheets is disclosed. The apparatus includes a rivet assembly for driving a piercing rivet into stacked metal sheets and a die for assisting in supporting the sheets during driving of the rivet and for assisting in securing the rivets to the sheets. The rivet of the invention includes an adhesive that is forced through passages in the rivet for assisting in fastening the rivet to the sheets and for assisting in fastening the sheets to each other with greater strength.

TECHNICAL FIELD

The present invention relates to a rivet and method for riveting metalmembers together for assembling automotive vehicle structures.

BACKGROUND OF THE INVENTION

It is known that the manufacture of automotive vehicles often requiresthat metal members be attached to each other to form automotive vehiclestructures. Pierce riveting is one potential method of attaching suchmembers, particularly, metal sheets. Pierce riveting typically requiresa sharpened end portion of a rivet to pierce through a first of twostacked metal sheets, and through at least a portion of a second of thestacked sheets. During such piercing, the sharpened end portion of therivet is typically deformed or bent to secure the rivet to the sheets.For conventional pierce riveting processes, however, large amounts offorce may be required to pierce the sheets. Moreover, such processestypically rely solely on a mechanical interlock of the rivet to securethe sheets together and may not secure the sheets together with adesired amount of strength. Therefore, there is a need for improvedpierce riveting techniques, apparatuses or both, for achieving highintegrity attachment of metal members such as metal sheets.

SUMMARY OF THE INVENTION

The present invention meets these needs by providing an improved methodof riveting a first metal member to a second metal member, withparticular utility in the formation of components for an automotivevehicle. The method involves riveting the members by providing apiercing rivet having a central axis, a generally disk-shaped headportion and an annular portion extending outwardly from a bottom surfaceof the head portion. The annular portion defines a cavity and aplurality of passages extend through the annular portion. An adhesive ina flowable state is disposed in the cavity of the annular portion. Forriveting, a first metal member is stacked on a second metal member,wherein each of the members has a first side and a second side, and atleast a portion of the second side of the first member is in overlappingcontact with at least a portion of the first side of the second memberfor forming an overlapped region. The first and second metal members areplaced between a rivet assembly and a die, the rivet assembly includinga punch, the die having a cavity. Thereafter, the rivet is driventhrough the first metal member and partially through the second metalmember in the overlapped region. During driving, the annular portion ofthe rivet is deformed radially outward away from the central axis of therivet to interferingly secure the rivet to the members thereby attachingthe members to each other. The adhesive is forced out of the cavitythrough the plurality of passages of the rivet thereby positioning theadhesive between an outer annular surface of the rivet and portions ofthe first member and the second member. Thereafter, the adhesive iscured to adhesively secure the rivet to the first and second members.

The present invention also provides a rivet for riveting a first metalmember to a second metal member. The rivet includes a generallydisk-shaped head portion disposed about a central axis and having asubstantially flat top surface and a generally conical bottom surface.The rivet also has an annular portion centered about the central axisand extending outwardly from a bottom surface of the head portion. Theannular portion includes an outer annular surface and a sharpenedpiercing edge. The annular portion also includes an inner annularsurface at least partially defining a substantially cylindrical cavitywithin the annular portion. A plurality of passages are radiallydisposed in the annular portion and extend from the inner surface to theouter surface. Moreover, the rivet is adapted to receive an adhesive ina flowable state in the cavity of the annular portion such that theadhesive may be forced through the plurality of passages to adhesivelysecure to the outer annular surface of the rivet and to the first andsecond members.

The present invention thus provides an improved rivet and rivetingtechnique for providing securing piercing rivets in stacked membersthereby more securely fastening the members together. The ability tocombine the mechanical interlock of a rivet with the additionalfastening strength of an adhesive creates particularly high integrityjoints for securing stacked members together.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of the present invention willbecome apparent upon reading the following detailed description incombination with the accompanying drawings, in which:

FIG. 1 is a sectional view of a riveting apparatus prior to riveting apair of stacked metal sheets to each other;

FIG. 2 is a sectional view of the riveting apparatus of FIG. 1 duringriveting of the pair of stacked metal sheets to each other;

FIG. 3 is a sectional view of the riveting apparatus of FIG. 1 furtheralong in the riveting of the pair of stacked metal sheets to each other;

FIG. 4 illustrates the riveting apparatus of FIGS. 1, 2 and 3 with arobot arm and an energy source;

FIG. 5(a) illustrates a side sectional view of an exemplary rivet;

FIG. 5(b) illustrates a bottom sectional view of the rivet of FIG. 5(a)taken along line 5B—5B;

FIG. 6(a) illustrates a side sectional view of another exemplary rivet;and

FIG. 6(b) illustrates a bottom sectional view of the rivet of FIG. 6(a)taken along line 6B—6B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1-3, a first metal member (depicted as a sheet 10) isriveted to a second metal member (also depicted as a sheet 12) with apiercing rivet 14 that is driven into the sheets 10, 12 by a rivetingapparatus 16. The riveting apparatus 16 includes a rivet drivingassembly 18 for driving the rivet 14 through the first sheet 10 and intothe second sheet 12 and a die 22 for supporting the metal sheets 10, 12and for assisting in securing the rivet 14 to the sheets 10, 12.

The rivet assembly 18 includes a clamp 24 (e.g., a generally elongatedmetal binder clamp) having an opening 26 extending down at least aportion of a length of the clamp 24. A punch 28 (e.g., an elongatedcylindrical steel punch) of the assembly 18 is received in the opening26 and the punch 28 is moveable along a length of the opening 26between, for example, at least a first position, as shown in FIG. 1, anda second position, as shown in FIG. 3. The punch 28 may be movedhydraulically, mechanically, electrically, pneumatically or otherwise.

In FIGS. 1-3, the punch 28, the opening 26 and the binder clamp 24 aregenerally cylindrical, coaxial or both about an axis 38 extendingcentrally along their lengths. Optionally, a housing (not shown) can beused to house or fasten the binder clamp 24 and the punch 28 together.Alternatively, other conventional fasteners or fastening techniques maybe used.

The die 22 includes a central cylindrical opening or cavity 46 definedby a bottom circular surface 48 and a peripheral annular wall surface50, which may be integrated into a single continuous surface.Preferably, the die 22 includes a protrusion 52 that extends into thecavity 46 from the center of the circular surface 48. Alternatively, thedie 22 may be formed in a variety of sizes or with a variety of cavityshapes depending upon the rivet 14 to be driven into the sheets 10, 12,the properties of the sheets 10, 12, the thickness of the sheets or acombination thereof. Preferably, the die 22 is supported by tooling, astand or the like.

The rivet assembly 18, the die 22 or both may be mounted to variousapparatus for moving the rivet assembly 18 or the die 22 relative toeach other, such as robots, C-frames or hard tooling such as a die set.In the exemplary embodiment shown in FIG. 4, the rivet assembly 18 isattached to a robot arm 60 that can move the rivet assembly 18 as neededor desired. The die 22 is positioned adjacent the robot arm 60.

Referring now to FIGS. 5(a)-5(b), there is shown a piercing rivet 14that is substantially symmetrical about a central axis 68 and includes ahead portion 70 and a body portion 72 with a sharpened edge portion 74,that is adapted to both pierce a material and deform during piercing forforming an interlock. The head portion 70 is generally disk-shaped witha substantially flat top surface 76 and a generally conical bottomsurface 78. The body portion 72 is generally annular and extendsoutwardly away from the bottom surface 78 of the head portion 70.Preferably, the head portion 70 extends radially outwardly away from thecentral axis 68 further than the body portion 72.

The body portion 72 includes an inner annular surface 80 and an outerannular surface 82. The inner annular surface 80 at least partiallydefines a central substantially cylindrical cavity 84 within the rivet14. Preferably, the body portion 72 includes a plurality of passages 88extending radially away from the central axis 68 and extending from theinner surface 80 to the outer surface 82.

The rivet 14 may be formed of a variety of high strength to weightmetals such as aluminum or magnesium alloys. Preferably, however, therivet 14 is formed of a mild or high strength steel. Optionally, therivet 14 may be coated with a suitable protective coating, such as ananti-corrosion agent, or may be selectively hardened at certain portionsfor achieving a hardness gradient in the rivet.

An amount of adhesive 90 is disposed within the cavity 84 for assistingthe rivet 14 to securely join the sheets 10, 12 together as furtherdescribed below. Preferably, the adhesive 90 is epoxy-based and has theability to adhere securely to one or more metals. In one embodiment, theadhesive 90 is generally flowable at temperatures typically experiencedin an automotive assembly plant (e.g., about 10° C. to about 40° C.) andcures to a hardened state at elevated temperatures (e.g., about greaterthan 100° C.). One example of a commercially available adhesive is soldunder the tradename BETAMATE 4601 and is commercially available from theDow Chemical Corporation, Midland, Mich.

Referring additionally to FIGS. 1-3, the piercing rivet 14 is positionedwithin the rivet assembly 18 for allowing the punch 28 to drive therivet 14 into the sheets 10, 12. As shown, the top surface 76 of therivet 14 is contacted substantially flush against the punch 28. Therivet 14 may be temporarily secured against the punch 28, such as bymagnetic forces, with a securing member (not shown) or otherwise.

The first metal sheet 10 and second metal sheet 12 each include a firstside 100 and a second side 102. The first sheet 10 is stacked upon thesecond sheet 12 such that at least a portion of the second side 102 ofthe first sheet 10 is in substantially continuous contact with at leasta portion of the first side 100 of the second sheet 12 to form anoverlapping portion or region for receiving the rivet 14. The sheets 10,12 may be formed of the same or different of several metals. Preferably,the sheets 10, 12 are formed of metal alloys of aluminum, magnesium,steel of various strengths or the like with thicknesses ranging between0.6 mm and 3.0 mm, although thicker of thinner sheets may also be used.

The stacked sheets 10, 12 are placed between the rivet assembly 18 andthe die 22 of the riveting apparatus 14. Preferably, the sheets 10, 12are placed upon the die 22 such that the second side 102 of the secondsheet 12 contacts the die 22. Thereafter, the rivet assembly 18 iscontacted with first side 100 of the first sheet 10 (e.g., using therobot arm 60 or another apparatus) to clamp the sheets 10, 12 betweenthe rivet assembly 18 and the die 22.

Once the sheets 10, 12 are clamped, the punch 28 is moved from its firstposition shown in FIG. 1 to its second position as shown in FIG. 3 todrive the rivet 14 at least partially through the overlapping region ofthe sheets 10, 12. As shown, the sharpened piercing edge 74 of the rivet14 pierces entirely through the first sheet 10 and partially through thesecond sheet 12.

During driving of the rivet 14, the rivet 14 urges a portion 120 of thefirst and second sheets 10, 12 into contact with the protrusion 52 ofthe die 22 thereby pinching the portion 120 between the rivet 14 and theprotrusion 52. In turn, the protrusion 52 places a force on the portion120 of the sheet 10, 12 and the force is transmitted to the annularportion 72 of the rivet 14. This force at least partially bends ordeforms the annular portion 72, starting with the sharpened edge 74,radially away from the central axis 68 of rivet 14 to interferinglysecure the rivet 14 to the sheets 10, 12 thereby attaching the sheets10, 12 to each other. Preferably, the rivet 14 is driven through thefirst sheet 10 and into the second sheet 12 until the top surface 76 ofthe head portion 70 is substantially flush with the first surface 100 ofthe first sheet 10.

Additionally, during driving of the rivet 14, the portion 120 of thesheets 10, 12 that contacts the protrusion 52 of the die 22 is pushedinto the cavity 84 of the rivet 14 thereby forcing the adhesive 90 outof the cavity 84. The adhesive 90 is either forced through the passages88 of the rivet 14, around the sharpened edge 74 of the rivet 14 or boththereby positioning the adhesive 90 between the outer annular surface 82of the rivet 14 and portions of the first sheet 10, the second sheet 12or both. The adhesive 90 may also be at least partially sandwichedbetween the second surface 102 of the first sheet 10 and the firstsurface 100 of the second sheet 12.

Thereafter, the adhesive 90 is cured to more securely attach the rivet14 to the sheets 10, 12 and to more securely attach the sheets 10, 12 toeach other. Preferably, the adhesive 90 cures after exposure to elevatedtemperatures of about 130° C. to about 220° C., and more preferablytemperatures of about 160° C. to about 180° C. and most preferably about170° C. Cure times may range, but are preferably less than 60 minutes,more preferably between about 20 and 40 minutes and most preferablyabout 25 minutes. Such time lengths and elevated temperatures aretypically encountered during a baking cycle during painting of theautomotive vehicle.

Advantageously, riveting of the sheets 10, 12 while simultaneouslyadhesively securing the rivet 14 to the sheets 10, 12 fastens the rivet14 more securely to the sheets 10, 12 thereby more securely fasteningthe sheets 10, 12 together.

In FIGS. 6(a) and 6(b), there is illustrated an alternative rivet 14substantially identical to the rivet 14 of FIGS. 5(a) and 5(b) with theexception that a plurality of channels 110 have been defined within theinner annular surface 80. Preferably, each of the channels 110 extendsfrom adjacent the bottom surface 78 of the head portion 70 of the rivet14 to one of the plurality of passages 88. Advantageously, the channels110 assist the adhesive 90 to flow through the passages 88 toward theouter annular surface 82 of the rivet 14.

In alternative embodiments, the overlapped region of the sheets 10, 12into which the rivet 14 is driven may be heated prior to driving therivet 14 through the sheets 10, 12. As an example, an electric currentmay be passed through the sheets 10, 12 according to methods such asthose disclosed in commonly owned copending application titled “A Methodand Apparatus for Riveting Metal Sheets”, U.S. Ser. No. 10/094,128 filedon the same date as the present application and fully incorporatedherein by reference for all purposes.

The rivet and method described above may be used for attaching severaldifferent automotive components that have sheet metal or sheet metalportions. Resulting joints are also considered part of the presentinvention. Examples include peel joints, lap joints, various vehiclepanels such as body panels, door panels, decklids, hoods, door frames,sunroof applications or the like. Furthermore, the overlapped regions ofthe sheets may be continuously bonded or intermittently bonded over someor all of its area.

It will be appreciated as well that the present invention is not limitedto joining metal sheets, but may be employed to join members in adifferent form or material.

It should be understood that the invention is not limited to the exactembodiment or construction which has been illustrated and described butthat various changes may be made without departing from the spirit andthe scope of the invention.

What is claimed is:
 1. A method of riveting a first member to a secondmember, comprising the steps of: (a) providing a piercing rivet having acentral axis, a head portion and an annular portion extending outwardlyfrom a bottom surface of the head portion wherein; (i) the annularportion defines a cavity; (ii) at least one passage extends through theannular portion; and (iii) an adhesive in a flowable state is disposedin the cavity of the annular portion; (b) placing the first member onthe second member, wherein each of the members has a first side and asecond side, and at least a portion of the second side of the firstmember is in overlapping contact with at least a portion of the firstside of the second member for forming an overlapped region; and c)driving the rivet through the first member and at least partiallythrough the second member in the overlapped region wherein; (i) theannular portion of the rivet is deformed radially away from the centralaxis of rivet to interferingly secure the rivet to the members therebyattaching the members to each other; and (ii) the adhesive is forced outof the cavity of the rivet through the passage of the rivet therebypositioning the adhesive between an outer annular surface of the rivetand portions of the first member and the second member; and (d) curingthe adhesive to adhesively secure the rivet to the first and secondmembers.
 2. A method as in claim 1, wherein the rivet is formed of atleast one metal alloy including a base metal selected from the groupconsisting of steel, aluminum and magnesium.
 3. A method as in claim 1,wherein a punch is electrically actuated for driving the rivet throughthe members.
 4. A method as in claim 1, wherein the adhesive is an epoxythat cures at temperatures from about 130° C. to about 220° C.
 5. Amethod as in claim 1 wherein the adhesive is curable in less than 60minutes.
 6. A method as in claim 1 wherein the first and second membersare formed of metal.
 7. A method as in claim 6 wherein the adhesive isadditionally located between a portion of the members after driving ofthe rivet.
 8. A method of riveting a first sheet to a second sheet,comprising the steps of: a) providing a piercing rivet having a centralaxis, a head portion and an annular portion extending outwardly from abottom surface of the head portion wherein; (i) the annular portionincludes an outer annular surface and a sharpened piercing edge; (ii)the annular portion includes an inner annular surface at least partiallydefining a substantially cylindrical cavity within the annular portion;(iii) a plurality of passages are radially disposed in the annularportion and extend from the inner surface to the outer surface; and (iv)an adhesive in a flowable state is disposed in the cavity of the annularportion; (b) stacking a first sheet on a second sheet, wherein each ofthe sheets has a first side and a second side, and at least a portion ofthe second side of the first sheet is in overlapping contact with atleast a portion of the first side of the second sheet for forming anoverlapped region; (c) placing the first and second sheets between arivet assembly and a die, the rivet assembly including a punch, the diehaving a cylindrical cavity with a protrusion extending into the cavity;and (d) driving the rivet through the first metal sheet and partiallythrough the second metal sheet in the overlapped region wherein; (i) theannular portion of the rivet is deformed radially away from the centralaxis of rivet to interferingly secure the rivet to the sheets therebyattaching the sheets to each other; and (ii) the adhesive is forced outof the cavity through the passages of the rivet thereby positioning theadhesive between the outer annular surface of the rivet and portions ofthe first sheet and the second sheet; e) curing the adhesive toadhesively secure the rivet to the first and second sheets.
 9. A methodas in claim 8 wherein the rivet is formed of at least one metal alloyincluding a base metal selected from the group consisting of steel,aluminum and magnesium.
 10. A method as in claim 8 wherein the punch iselectrically actuated for driving the rivet through the sheets.
 11. Amethod as in claim 8 wherein the adhesive is an epoxy that cures attemperatures from about 130° C. to about 220° C.
 12. A method as inclaim 8 wherein the adhesive is curable in less than 60 minutes.
 13. Amethod as in claim 8 wherein the first and second sheets are formed ofmetal.
 14. A method as in claim 13 wherein the adhesive is additionallylocated between a portion of the sheets after driving of the rivet.